The microcirculation and correlated histology of healing bone, under different conditions of repair, are being investigated against the background of the normal circulation in laboratory animals. Microangiography is the chief investigative tool in survival experiments of different durations, mainly on dogs. Standard histologic, tetracycline fluorophore and blood-flow observations are included. The results of fracture, osteotomy, internal fixation, bone grafting, implantations of foreign materials, and thermal necrosis of bone are being examined. The objectives of the project are to describe and document the vascular and histologic details of the reparative processes of bone as similar to human bone as possible, and to show the clinical applications.